Impact absorber

ABSTRACT

The invention concerns an impact-absorption device, particularly for vehicles, which is attached on one side to the bumper and on the other side to the longitudinal girder or another part of the vehicle-body structure. The device has a non-regenerative deforming unit designed to absorb energy when acted on by a force with a component in the direction of the longitudinal axis of the longitudinal girder. The deforming unit has at least two hollow deforming elements which engage one inside the other, one of which being attached to the bumper while the other is attached to the longitudinal girder of the vehicle. If the device is crushed by a force component acting along its longitudinal axis, the deforming elements are telescoped into each other, deforming the material. The hollow deforming elements (12, 14) have a non-circular, preferably oval or angular, cross-section. In a particularly preferred embodiment, the hollow elements have ribs.

FIELD OF THE INVENTION

The invention concerns an impact absorber, especially for motorvehicles, which is attached to the bumper on one side and to thelongitudinal runner of the vehicle chassis on the other side, with anon-regenerable deformation member to absorb kinetic energy ifcompressive forces are applied in the direction of the longitudinal axisof the longitudinal runner.

BACKGROUND

Generic impact absorbers are known from DE-OS 38 36 724, EIPPER et al.,and also from DE-OS 30 42 931, URSPRUNG et al., for example. These knownimpact absorbers are disadvantageous because they are complicated tomanufacture and are therefore relatively expensive.

Furthermore, impact absorbers consisting of pipe-shaped parts whichslide into each other under deformation, with essentially circularcross-sections are known from U.S. Pat. No. 3,899,047, MAEDA, and DE-PS28 25 460, LINDBERG, and corresponding U.S. Pat. No. 4,181,198.

These known impact absorbers worked well in case of pure head-oncollisions, but were not equipped to accept crosswise forces in asatisfactory manner in case of offset head-on collisions which occur farmore frequently in practice.

SUMMARY OF THE INVENTION

As a consequence, it is the purpose of the invention to provide aneffective impact absorber which is also more effective in case of forcesoccurring at an angle, compared to the known impact absorbers.

The problem is solved in accordance with the invention with a genericimpact absorber, in which the hollow deformation pieces have anon-round, preferably oval or rectangular cross-section.

It is most often expected of impact absorbers, that they accept forceswhich occur essentially in a plane, so that an oval shape is adequate inmost cases. For specially positioned cases, other non-round shapes canalso be formed however.

It can thereby be in the interest of saving materials and weight if bothof the hollow parts have lengthwise ribs shaped as reinforcementprofiles to act as reinforcements, which can significantly improve themechanical stability of the impact absorbers with the same weight. Thisform of implementation can be manufactured especially with the internalhigh pressure moulding process, as it is described in the following, forexample.

It can be preferable to provide at least one intermediate layer betweenthe outer deformation piece and the inner deformation piece, which canbe deformed elastically or inelastically.

Depending on the required characteristics of the impact absorber, it ispossible to shape the fixture in such a way that elastic deformationtakes place up to a predetermined impulse in the longitudinal direction,while irreversible deformation takes place with higher impulses.

With certain forms of implementation, it can also be worthwhile howeverto provide inelastically deformable areas.

In addition to the close fit of the hollow moulded parts shaped mutuallyinside each other, it can be provided that the inner and outer layersare connected to each other through means of connection, such as weldpoints, rivets, pins or adhesive. Through such means of attachment, itis possible to vary the response characteristic of the absorber further,as is well-known to experts.

Preferably, the deformation piece has a deformation cone or crumple zonewhose angle alpha is self-restraining for the displacement of the outerand inner parts relative to each other.

In general, it is to be established that pipes which are partiallylocated inside each other are Used as the starting materials for themanufacture of the impact absorber. "Pipe" is to be understood here as ahollow body which has a small inside diameter compared with its lengthand this expression is not restricted in any way to hollow bodies withcircular cross-sections, but also includes rectangular pipes, hexagonalpipes and other hollow bodies with non-circular cross-sections, whoselengthwise dimension is larger than their diameter.

A seamless pipe is preferred as the starting pipe. Seamless pipe is tobe understood here as pipe which does not exhibit a weld seam in theusual meaning.

Preferably, the starting pipes for the impact absorber in accordancewith the invention--whereby the intermediate layer can also bemanufactured from a pipe-shaped starting piece or can already be appliedas the outside layer on the starting inner pipe or as the inside layeron the starting outer pipe--consist of multiple metal pipes arrangedinside each other, but not necessarily overlapping each other exactly,whereby the metal of the metal pipes can be the same or different andthe material for the intermediate layer can also be non-metallic. Afterimplementation of the process, meaning after the application of internalpressure on the different pipe layers, they are pressed onto one anotherand fitted onto each other tightly and run essentially parallel to eachother through close fit and friction fit, possibly also with shapedribs. At the same time, other materials such as rubber and plastics, forexample, can also be moulded with the metal, provided that they aresuitable for the moulding process and metal pipes should also beunderstood here as pipes which consist only partly of metal and can alsoexhibit one or more other materials in layers. For example, suitablemetals are carbon steels and alloyed steels, high temperature steels,annealing steels, unalloyed and alloyed, high temperature steels andstainless steels; furthermore, aluminum, aluminum alloys; titanium andtitanium alloys, copper and its alloys as well as nickel and similarmaterials, whereby it is preferable that the materials guarantee anextensive contour-true filling of the tool mould. A low yield stress, ahigh deformability and a suitable strength after the moulding processare required in many cases with steel materials.

In one particular preferred process for the manufacture of an impactabsorber in accordance with the invention, a multi-walled deformationpiece is manufactured through an internal high pressure moulding processin which a fluid medium is introduced into an essentially pipe-shaped,multi-walled starting material under high pressure and thereby shapesthe starting material against an outer mould. This process makespossible rapid and problem-free manufacture of deformation piecesadapted to each other, which are already located in their finalinstallation position, through which complicated steps to insert theindividual pieces within each other and also high requirements on theexact fit of the inner and outer parts can be avoided or fulfilled withno problems through the process.

The internal high pressure moulding process used here is described forexample in "Industrieanzeiger" No. 20 of 9 Mar. 1984 and also in"Metallumformtechnik", Issue 1D/91, P. 15 ff: A. Ebbinghaus: "PrecisionWorkpieces in Light Construction, Manufactured Through Internal HighPressure Mouldings", and also "Werkstatt und Betrieb" 123 (1990), 3, P.241-243: A. Ebbinghaus: "Economic Construction with Internal HighPressure Moulded Precision Workpieces" and also "Werkstatt und Betrieb"122 (19910), 11 (1989), P. 933-938. Reference is made here to thesepublications to avoid repetition in the full extent.

It is preferable thereby to use an internal high pressure mouldingprocess in which the fluid material is a material on a water basis undera pressure up to 10,000 bar.

Preferably at least the inner and the outer parts are made of metal,preferably steel.

It can be provided that the elastic intermediate layer consists of arubber-elastic material, such as a polymer, silicon rubber or rubber.

A suitable material for an intermediate layer in a form of executionwith an inelastic intermediate layer is soft metal or plastic, forexample.

In case of a design of the impact absorber with multiple pieces,especially one with more than two parts, each layer can each bemanufactured from the material most suitable for it, whereby the innerand the outer materials must fulfill the requirements of a mechanicallyresistant, partially elastic material, while the material for theintermediate layer can serve to absorb energy and can be deformableeither elastically or inelastically-- depending on the desired dampingbehaviour.

DRAWINGS

FIG. 1 Shows a schematic representation of an impact absorber inaccordance with the invention,

FIG. 2 Shows a cross-section along Line 2--2 of the impact absorber inFIG. 1,

FIG. 3 Shows a further impact absorber with shaped reinforcing ribs,

FIG. 4 Shows a cross-section through the impact absorber in FIG. 3 alongLine 4--4;

FIG. 5 Shows an impact absorber with shaped crosswise ribs, in aperspective view,

FIG. 6 Shows a lengthwise section of the impact absorber of FIG. 5.

DETAILED DESCRIPTION

As shown in FIG. 1, an impact absorber 10 in accordance with theinvention exhibits a combination of hollow parts consisting of twohollow parts partially inserted into each other, an inner deformationpiece 14 and an outer deformation piece 12. Both parts are shapedconically in their mutual overlapping area to the outside in bulgingform under a self-restraining angle alpha which prevents the two piecesfrom separating from each other in case of pressure or tension below apredetermined force. Preferably both parts are made of steel and arepreferably manufactured through the well-known internal high pressuremoulding process, preferably from starting pipe pieces inserted intoeach other, through the application of pressure through a fluid mediumfrom the inside of the pipe together against an outer mould, so thatboth parts are bonded onto each other through close fit and frictionfit. In the form of implementation presented here, the inner part isattached to the body, preferably to a longitudinal runner of thechassis, while the outer part is connected to the bumper. When an impactoccurs, such as head-on collision or an offset impact with a forcecomponent in the direction of the longitudinal axis of the vehicle, theinner and outer deformation parts (12, 14) are pushed against each otherwith the deformation of the bulge area to the outside and a widening ofthe angle alpha until the ability of the impact absorber to deform isexhausted and the deformation forces work further on the chassis andbumper, whereby the energy absorbed by the impact absorber can beadapted to meet the requirements through the selection of an appropriateprofile in the overlapping area.

FIG. 2 shows a cross-section through the impact absorber in FIG. 1 alongthe Line 2--2, from which the oval-shaped cross-section can be seen.FIG. 3 presents a cross-section of a further form of implementation ofan impact absorber 10 in accordance with the invention, which haslengthwise ribs.

In addition to the connection of the layers through the close fit andfriction fit resulting from the shaping, a further connection betweenthe layers can be established through weld points, adhesives, rivets orsimilar means in order to control the displacement of the parts relativeto each other.

FIG. 3 contains a perspective view of an impact absorber 10, which isreinforced by shaped ribs in the lengthwise direction. This design makesit possible to lend the material an increased stiffness and resistanceto pressure in the longitudinal direction of the impact absorber andthereby, in contrast to the form of implementation with uniformly thickwalls, to use less material with the advantages of the correspondingmaterial savings and weight reduction.

A cross-section along Line 4--4 in FIG. 3 is shown in FIG. 4, from whichit can be clearly seen that the shaping of the impact absorber inaccordance with the invention through the internal high pressuremoulding process now produces a parallel wall shape in the inner andouter parts, so that the ribs 20 are formed in both parts.

FIG. 5 contains a perspective view of a further form of implementationof the impact absorber with multiple cross ribs, which serve as intendedcrushpoints 22 and thereby facilitate deformation of the impact absorberat preferred locations, through which it is possible to control thebehavior of this impact absorber in case of a head-on collision andfurther kinetic energy can be absorbed through deformation of the impactabsorber, without transmitting the impact directly in the direction ofthe impact.

A cross-section of the impact absorber presented in FIG. 5 can be seenin FIG. 6, which shows that the inner and outer parts which form theimpact absorber run parallel to each other, so that the intendeddeformation takes place in the area of the crosswise ribs in case of aforce in the direction of the longitudinal axis.

What is claimed is:
 1. Impact absorber for a motor vehicle having achassis, including a lengthwise frame member, and a bumper;said impactabsorber interconnecting said bumper and said lengthwise frame member,and including a non-regenerable deformation member to absorb kineticenergy if forces are applied in the direction of a longitudinal axis ofthe lengthwise frame member, whereby the deformation member has at leasttwo telescopically arranged hollow deformation pieces (12, 14), of whicha first one is an outer deformation piece (12) and a second one is aninner deformation piece (14), of which one is attached to the bumper andthe other is attached to the lengthwise frame member of the vehicle,whereby the deformation pieces (12, 14) are pushed together relative toeach other with material deformation in case of crushing of the impactabsorber with a force component along its longitudinal axis, and whereinthe hollow deformation pieces (12, 14) have a non-circular cross-sectionin a vertical plane located between said bumper and said vehiclechassis.
 2. Impact absorber in accordance with claim 1, whereinthehollow deformation pieces are both formed with lengthwise reinforcingribs.
 3. Impact absorber in accordance with claim 1, whereinthe hollowdeformation pieces each have at least one crosswise rib (22).
 4. Impactabsorber in accordance with claim 1, whereinat least one of the outerdeformation piece (12) and the inner deformation piece (14) has acoating which prevents corrosion and influences how easily they slidewith respect to each other.
 5. Impact absorber in accordance with claim1, whereinthe hollow deformation pieces have a common longitudinal axisand taper with respect to said axis at an angle which is not greaterthan 30°.
 6. Impact absorber in accordance with claim 1, whereinthehollow inner deformation member (14) defines hollow spaces which arefilled with a compressible energy-absorbing medium.
 7. Impact absorberin accordance with claim 1, whereineach deformation piece (10) ismanufactured through an internal high-pressure molding process in whicha fluid medium is introduced under high pressure into an essentiallypipe-shaped multi-walled starting material and the starting material isshaped through pressure against an outer mold.